The present invention generally relates to a dual fuel internal combustion engine selectively combusting first fuel and second fuel, and more particularly relates to switching fuel for a dual fuel internal combustion engine selectively combusting gasoline and gaseous hydrogen.
In recent years, for a lower tailpipe emission from internal combustion engines, dual fuel engines using together gaseous fuel, such as compressed natural gas, liquidized propane gas, or compressed hydrogen, and gasoline have been developed. For example, in Japanese patent application publication no. H03-26835, a dual fuel engine using together gasoline and gaseous hydrogen is described. Also, disclosed in Japanese patent application publication no. H11-311136 is a hybrid automotive vehicle using an electric motor as well as a dual fuel engine using bi-fuel of gasoline and gaseous hydrogen to drive the vehicle.
In a dual fuel engine that is capable of combusting gaseous hydrogen and/or gasoline, fuel injected into the engine cylinders or combustion chambers may be switched from gasoline to gaseous hydrogen. During the transition from gasoline to hydrogen, the initial charge may be ignited earlier than desired, thereby increasing temperature and pressure within the intake manifold. In particular, combustion of gasoline can elevate the temperature of certain combustion chamber surfaces and may also produce residual uncombusted carbon or other matter. These elements that remain in the combustion chamber may cause some of the injected hydrogen to increase temperature and pressure in the intake system. Furthermore, it may be possible during such conditions to combust gasoline that may remain in the intake manifold from prior gasoline injections (abnormal combustion).
Therefore, the inventors herein have recognized the above-mentioned disadvantages and has developed a method to transition an internal combustion engine from gasoline operation to hydrogen operation that offers substantial improvements.